Only element in xslt result set is not the last element? - xslt-2.0

Question

I have the following snippet
<xsl:for-each select="book">
<xsl:value-of select="title"/><xsl:if test="position() != last()">,</xsl:if>
</xsl:for-each>
I want it to be a list of comma-separated book titles.
The output is correct when I have no books in the list. It is also correct when I have more than one book.
However, if I have exactly one book, it prints a comma at the end.
When I change the condition to only print a comma if it is the last element, the case where there is only one book doesn't print a comma.
So it seems like when there is only one element it is not treated as the last element. How can I deal with this?
Sample XML: looks something like this
<booklist>
<book>
<title>My book</title>
<author>Some author</author>
</book>
<book>
<title>Another book</title>
<author>Another author</author>
</book>
</booklist>
When there are two books in the list, I get
My book, Another book
When I delete the second entry, I get
My book,
EDIT:
I found the issue. I was using an <xsl:apply-templates> to select a set of data, and then inside another template for each book, I was doing the position check. However, last() was referring to the original set of data and not the filtered subset.

Answer 1

The following works fine for me in Firefox (I get no commas for no books, and n-1 commas for n books if n>0). I suspect your XSLT processor is broken.
The XSLT ("x.xsl"):
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="html" indent="yes" encoding="iso-8859-1" media-type="text/xhtml" doctype-public="-//W3C//DTD HTML 4.0//EN"/>
<xsl:template match="/">
<xsl:for-each select="root/book">
<xsl:value-of select="title"/><xsl:if test="position() != last()">;</xsl:if>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
The XML:
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet href="x.xsl" type="text/xsl"?>
<root>
<book>
<title>A</title>
</book>
<book>
<title>B</title>
</book>
</root>

Answer 2

What's "test()"? I think you want "last()-1".